The long-term goal of the proposed research is to further our understanding of N-type Ca2+ channel modulation by opioid receptor-like 1 (NOP, or OP4) opioid receptors in rat stellate ganglion (SG) neurons involved in pain signaling. This project will focus on identifying the specific signal transduction elements that contribute to NOP receptor desensitization, the pharmacological profile of constitutively active receptors and N-type Ca2+ channel inhibition. The NOP receptor is activated by the endogenous peptide nociceptin FQ (N/OFQ). N/OFQ-activated NOP receptors can exert algesic or analgesic effects in animal pain models. Clinical studies have shown that SG blockade can be used to treat patients that suffer from chronic facial pain or headaches. A combination of electrophysiological, immunofluorescence, and molecular techniques will be used to probe the mechanisms by which NOP receptors modulate N-type Ca2+ channels. The specific aims of this proposal are to: i) identify the specific Gb and Gg subunits that mediate N-type Ca2+ channel inhibition for N/OFQ-stimulated ii) identify the G protein-coupled receptor kinase (GRK) isoform that mediates desensitization of NOP receptors iii) to determine the interaction of GRK and Gb proteins with constitutively active NOP receptors, as well as to examine the pharmacological profile of the receptors. NOP receptors and N-type Ca2+ channels are known to participate in pain transmission. Thus, the proposed studies will help to clarify the signaling mechanisms underlying these processes and aid in the development of novel agents for the treatment of pain, such as those associated with chronic headache and complex region pain syndrome, and at the same time prevent opioid tolerance and addiction. PUBLIC HEALTH RELEVANCE: The purpose of this grant proposal is to examine the cellular mechanisms by which opiate receptors that are involved in pain processes regulate the entry of Ca2+ ions into nerves. We will identify specific cellular proteins that affect the functional response of these receptors, and we will also study the pharmacology of these receptors. These studies will lead to new information that can be employed to help treat pain without developing tolerance or opiate addiction.